Chloroprene polymer latex, rubber component, rubber composition, vulcanization molded body, and method for producing chloroprene polymer latex

Abstract

Provided is a chloroprene polymer latex which has excellent mechanical stability and excellent recovery efficiency of a rubber by means of freezing or the like. The present invention provides a chloroprene polymer latex which comprises micelles that each contain a chloroprene polymer and an emulsifier. The volume-based particle size distribution of the micelles is determined in the range of 1 nm to 10,000 nm by means of dynamic light scattering so as to obtain a histogram. The histogram takes particle diameters which are expressed by common logarithms on the horizontal axis, has 45 classes that are obtained by dividing the horizontal axis into 45 equal parts in the range of 1 nm to 10,000 nm, and takes the volume distribution on the vertical axis. If dk nm is the class value of the class k particle diameter that is the k-th smallest particle diameter, Vk is the volume distribution of the class k, S is the solid content ratio of the chloroprene polymer latex, ρLx g / cm3 is the specific gravity of the chloroprene polymer latex, ρCR g / cm3 is the specific gravity of the chloroprene polymer, n mol is the amount of the emulsifier contained in 1 L of the chloroprene polymer latex, and NA is the Avogadro number, the chloroprene polymer latex satisfies the following formula. [Mathematical formula 1]

Description

Chloroprene polymer latex, rubber component, rubber composition, vulcanized molded product, and method for producing chloroprene polymer latex

[0001] The present invention relates to a chloroprene polymer latex, a rubber component, a rubber composition, a vulcanized molded article, and a method for producing a chloroprene polymer latex.

[0002] Chloroprene-based rubbers have excellent mechanical properties, ozone resistance, and chemical resistance, and by utilizing these properties, they are used in a wide range of fields, such as automobile parts, adhesives, various industrial rubber parts, etc. For example, Patent Document 1 discloses a method for producing a chloroprene-based polymer, in which chloroprene or chloroprene and a monomer copolymerizable with chloroprene are polymerized in an aqueous medium in the presence of a surfactant, to which the surfactant has been added at a concentration less than the critical micelle concentration (CMC).

[0003] WO2011 / 004860

[0004] However, it has been difficult to obtain a chloroprene polymer latex that is excellent in mechanical stability and allows efficient recovery of rubber by freezing or the like.

[0005] The present invention has been made in view of the above circumstances, and provides a chloroprene polymer latex which has excellent mechanical stability and which allows efficient recovery of rubber by freezing or the like.

[0006] According to the present invention, there is provided a chloroprene polymer latex containing micelles containing a chloroprene polymer and an emulsifier, wherein the volume-based particle size distribution of the micelles is measured by dynamic light scattering in a range of 1 nm to 10,000 nm to obtain a histogram, the histogram having 45 classes obtained by equally dividing the horizontal axis into 45 classes in the range of 1 nm to 10,000 nm, the vertical axis representing the volume distribution, the class value of the particle size of the kth smallest class k being dknm, the volume distribution of class k being Vk, the solid content of the chloroprene polymer latex being S, and the specific gravity of the chloroprene polymer latex being ρ Ｌｘ　 g / cm ３ , the specific gravity of the chloroprene polymer is ρＣＲ g / cm ３ The amount of emulsifier contained in 1 L of the chloroprene polymer latex is n mol, Avogadro's number is N Ａ When the above formula is satisfied, a chloroprene polymer latex is provided which satisfies the following formula:

[0007] As a result of extensive investigations, the present inventors have found a chloroprene polymer latex which is excellent in mechanical stability and rubber recovery efficiency by freezing or the like, by defining a ratio of a micelle surface area to an emulsifier amount, which is calculated by a specific formula obtained from particle size distribution, and have thus completed the present invention.

[0008] Various embodiments of the present invention will be exemplified below. The embodiments shown below can be combined with each other. [1] A chloroprene polymer latex containing micelles containing a chloroprene polymer and an emulsifier, wherein the volume-based particle size distribution of the micelles is measured by dynamic light scattering in the range of 1 nm to 10,000 nm to obtain a histogram, the horizontal axis of the histogram representing particle diameters expressed in common logarithms, the horizontal axis having 45 classes obtained by dividing the range of 1 nm to 10,000 nm into 45 equal classes, the vertical axis representing volume distribution, and the class value of the particle diameter of the class k having the kth smallest particle diameter being d ｋ nm, the volume distribution of class k is V ｋ , the solid content of the chloroprene polymer latex is S, and the specific gravity of the chloroprene polymer latex is ρ Ｌｘ　 g / cm ３ , the specific gravity of the chloroprene polymer is ρ ＣＲ　 g / cm ３ The amount of emulsifier contained in 1 L of the chloroprene polymer latex is n mol, Avogadro's number is N Ａ A chloroprene polymer latex that satisfies the following formula when [2] The chloroprene polymer latex according to [1], wherein D50 obtained from the particle size distribution is 50 to 300 nm. [3] The chloroprene polymer latex according to [1] or [2], wherein the content of the emulsifier is 0.5 to 8.0 parts by mass based on 100 parts by mass of the chloroprene polymer. [4] The chloroprene polymer latex according to any of [1] to [3], wherein the chloroprene polymer latex has an aggregate generation rate of 0.5 to 25.0% in a mechanical stability test measured under conditions of a load of 1.0 kg, a rotation speed of 1,000 rpm, and a time period of 10 minutes. [5] The chloroprene polymer latex according to any of [1] to [4], wherein the micelle surface area per 1 L of the chloroprene polymer latex is 30,000 to 100,000 m ２ [6] A rubber component of the chloroprene polymer latex according to any one of [1] to [5]. [7] A rubber composition comprising the rubber component according to [6]. [8] A vulcanized molded article comprising the rubber composition according to [7]. [9] The vulcanized molded article according to [8], which is any one of a power transmission belt, a conveyor belt, a hose, a wiper, a dipped product, a sealing part, an adhesive, a boot, a rubber-coated fabric, a rubber roll, a vibration-proof rubber, and a sponge product.

[10] A method for producing a chloroprene polymer latex containing micelles containing a chloroprene polymer and an emulsifier, the method comprising: a monomer droplet micro-reducing step, a polymerization step, and an emulsifier additional-adding step; in the monomer droplet micro-reducing step, droplets containing a raw material monomer including a chloroprene monomer are collided with a collision medium in the presence of an initially-added emulsifier to reduce the droplets to an average particle size of 300 nm or less; in the polymerization step, the raw material monomer including the chloroprene monomer is polymerized to obtain a chloroprene polymer; and in the emulsifier additional-adding step, an additionally-added emulsifier is additionally added after the monomer droplet micro-reducing step, and the amount of the additionally-added emulsifier is 10 to 60% by mass relative to 100% by mass of the total of the initially-added emulsifier and the additionally-added emulsifier.

[0009] The chloroprene polymer latex according to the present invention can provide a chloroprene polymer latex that is excellent in mechanical stability and in rubber recovery efficiency by freezing or the like. In one embodiment of the present invention, a rubber component can be recovered from the chloroprene polymer latex to form a rubber composition. The chloroprene polymer latex has excellent stability during production, storage, and transportation, and the rubber component can be efficiently recovered, resulting in fewer defects in production, reduced costs and labor, and improved production efficiency. The rubber composition containing the rubber component can be formed into a vulcanized molded product, which can be suitably used as any of power transmission belts, conveyor belts, hoses, wipers, dipped products, sealing parts, adhesives, boots, rubber-coated fabrics, rubber rolls, vibration-proof rubber, and sponge products, for example.

[0010] The present invention will be described in detail below by illustrating embodiments of the present invention. The present invention is not limited by these descriptions. The features of the embodiments of the present invention described below can be combined with each other. Furthermore, each feature can be an invention independently.

[0011] 1. Chloroprene Polymer Latex The chloroprene polymer latex according to the present invention comprises micelles containing a chloroprene polymer and an emulsifier, and has a ratio of the micelle surface area to the amount of the emulsifier, which is calculated by a specific formula using values ​​obtained from a particle size distribution obtained under specific conditions, within a specific range.

[0012] 1.1 Chloroprene-Based Polymer The chloroprene-based polymer according to the present invention refers to a polymer containing a monomer unit (monomer unit = structural unit) derived from 2-chloro-1,3-butadiene (hereinafter also referred to as chloroprene). Examples of the chloroprene-based polymer include a chloroprene homopolymer and a chloroprene copolymer (a copolymer of chloroprene and a monomer copolymerizable with chloroprene). The polymer structure of the chloroprene-based polymer is not particularly limited.

[0013] Commercially available 2-chloro-1,3-butadiene may contain a small amount of 1-chloro-1,3-butadiene as an impurity. 2-chloro-1,3-butadiene containing such a small amount of 1-chloro-1,3-butadiene can also be used as the chloroprene monomer of this embodiment.

[0014] The chloroprene polymer according to one embodiment of the present invention may also have a monomer unit derived from a monomer other than a chloroprene monomer. The monomer other than a chloroprene monomer is not particularly limited as long as it is copolymerizable with the chloroprene monomer, and examples thereof include (meth)acrylic acid esters (methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc.), hydroxyalkyl (meth)acrylates (2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc.), unsaturated nitriles (acrylonitrile, methacrylonitrile, ethacrylonitrile, phenylacrylonitrile, etc.), 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene, sulfur, etc.

[0015] As an example, a chloroprene-based polymer according to one embodiment of the present invention may contain an unsaturated nitrile monomer unit. The content of the unsaturated nitrile monomer unit in the chloroprene-based polymer may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25% by mass, or may be within a range between any two of the values ​​exemplified here. When the content of the unsaturated nitrile monomer unit in the chloroprene-based polymer is equal to or less than the upper limit, the Mooney viscosity of the unvulcanized product can be maintained sufficiently low, while the water resistance and heat resistance of the vulcanized product of the rubber composition can be improved. The chloroprene-based polymer according to one embodiment of the present invention may contain an unsaturated nitrile monomer unit from the viewpoint of improving mechanical properties, dynamic properties, abrasion resistance, oil resistance, etc.

[0016] The content of unsaturated nitrile monomer units in a chloroprene polymer can be calculated from the content of nitrogen atoms in the chloroprene polymer. Specifically, the content of nitrogen atoms in 100 mg of chloroprene polymer can be measured using an elemental analyzer (Sumigraph 220F, manufactured by Sumika Chemical Analysis Center, Ltd.), and the content of structural units derived from unsaturated nitrile monomers can be calculated. Elemental analysis can be performed under the following conditions. For example, the electric furnace temperatures are set to 900°C for the reactor, 600°C for the reduction furnace, 70°C for the column, and 100°C for the detector, and oxygen is flowed at 0.2 mL / min as the combustion gas and 80 mL / min as the carrier gas. A calibration curve can be prepared using aspartic acid (10.52%), which has a known nitrogen content, as a standard substance.

[0017] As another example, a chloroprene polymer according to one embodiment of the present invention may contain a diene monomer unit. The content of the diene monomer unit in the chloroprene polymer may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30% by mass, or may be within a range between any two of the values ​​exemplified here. Examples of the diene monomer include conjugated diene monomers having 4 to 6 carbon atoms (excluding chloroprene), such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene.

[0018] A chloroprene-based polymer according to one embodiment of the present invention may contain 2,3-dichloro-1,3-butadiene monomer units. The chloroprene-based polymer according to one embodiment of the present invention may contain 0 to 30% by mass of 2,3-dichloro-1,3-butadiene monomer units relative to 100% by mass of the chloroprene-based polymer. The content of the 2,3-dichloro-1,3-butadiene monomer units may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30% by mass, or may be within a range between any two of the values ​​exemplified here.

[0019] For example, a chloroprene-based polymer according to an embodiment of the present invention may include an aromatic vinyl monomer unit. The content of the aromatic vinyl monomer unit in the chloroprene-based polymer may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30% by mass, or may be within a range between any two of the values ​​exemplified here. The aromatic vinyl monomer unit preferably includes styrene.

[0020] The chloroprene polymer according to one embodiment of the present invention preferably contains 70 to 100% by mass of chloroprene monomer units, where the chloroprene polymer is taken as 100% by mass. The content of chloroprene monomer units in the chloroprene polymer is, for example, 70, 75, 80, 85, 90, 95, or 100% by mass, and may be within a range between any two of the values ​​exemplified here. By setting the content of chloroprene monomer units within the above range, a rubber composition can be obtained that can give molded articles with excellent hardness, mechanical properties, etc.

[0021] A chloroprene polymer according to one embodiment of the present invention may contain 0 to 30% by mass of monomer units other than chloroprene monomer units, based on 100% by mass of the chloroprene polymer. The content of monomer units other than chloroprene monomer units and unsaturated nitrile monomer units in the chloroprene polymer may be, for example, 0, 5, 10, 15, 20, 25, or 30% by mass, and may be within a range between any two of the values ​​exemplified here. By adjusting the copolymerization amount of monomers other than chloroprene monomers to fall within the above range, the effects achieved by copolymerizing these monomers can be achieved without impairing the properties based on the chloroprene monomer units.

[0022] The chloroprene polymer latex according to one embodiment of the present invention may contain one or more chloroprene polymers. The chloroprene polymer latex according to one embodiment of the present invention may contain one chloroprene polymer. When the chloroprene polymer latex according to one embodiment of the present invention contains two or more chloroprene polymers, the content of each monomer unit based on the total amount of the two or more chloroprene polymers relative to 100% by mass of the total of the two or more chloroprene polymers contained in the chloroprene polymer latex is preferably within the above-mentioned range.

[0023] The chloroprene polymer (e.g., chloroprene homopolymer or chloroprene copolymer) included in the chloroprene polymer according to the present invention may be a sulfur-modified chloroprene polymer, a mercaptan-modified chloroprene polymer, a xanthogen-modified chloroprene polymer, a dithiocarbonate-based chloroprene polymer, a trithiocarbonate-based chloroprene polymer, or a carbamate-based chloroprene polymer.

[0024] The weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (polydispersity of molecular weight, Mw / Mn) of the chloroprene polymer may be within the following ranges, from the viewpoint of easily obtaining well-balanced mechanical properties and the like.

[0025] The weight average molecular weight of the chloroprene polymer is, for example, 10 × 10 ３ g / mol, 50×10 ３ g / mol, 100×10 ３ g / mol, 300×10 ３ g / mol, 400×10 ３ g / mol, 450×10 ３ g / mol, 500×10 ３ g / mol, 800×10 ３ g / mol, 1000×10 ３ g / mol, 2000×10 ３ g / mol, 3000×10 ３ g / mol, 5000×10 ３ g / mol and may be in the range between any two of the values ​​exemplified herein.

[0026] The number average molecular weight of the chloroprene polymer is, for example, 1 × 10 ３ g / mol, 5 x 10 ３ g / mol, 10×10 ３ g / mol, 50×10 ３ g / mol, 100×10 ３ g / mol, 130×10 ３ g / mol, 200×10 ３ g / mol, 300×10 ３ g / mol, 500×10 ３ g / mol, 800×10 ３ g / mol, 1000×10 ３ g / mol and may be in the range between any two of the values ​​exemplified herein.

[0027] The molecular weight distribution of the chloroprene polymer is 1.0, 1.5, 2.0, 2.5, 3.0, 3.2, 3.4, 3.5, 3.8, 4.0, 5.0, 8.0, or 10, and may be within a range between any two of the numerical values ​​exemplified here.

[0028] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the chloroprene polymer can be measured by gel permeation chromatography (GPC) and converted into polystyrene equivalents. Specifically, they can be measured by the method described in the examples.

[0029] 1.2 Emulsifier The chloroprene polymer latex according to the present invention contains an emulsifier. The emulsifier is not particularly limited, and known emulsifiers commonly used in chloroprene polymerization can be used. Examples of the emulsifier include anionic emulsifiers and nonionic emulsifiers. Examples of anionic emulsifiers include fatty acid salts such as potassium tallow fatty acid, partially hydrogenated potassium tallow fatty acid, potassium oleate, and sodium oleate; resin acid salts such as potassium rosinate, sodium rosinate, hydrogenated potassium rosinate, and hydrogenated sodium rosinate; alkyl sulfate salts such as sodium lauryl sulfate; alkyl benzene sulfonates such as sodium dodecyl benzene sulfonate; and sodium salts of β-naphthalene sulfonic acid formalin condensates. Examples of nonionic emulsifiers include polyethylene glycol ester emulsifiers and polyvinyl alcohol. The emulsifier preferably contains at least one of alkyl sulfate salts, alkyl benzene sulfonates, and resin acid salts, and more preferably contains at least one of alkyl sulfate salts and alkyl benzene sulfonates. The number of carbon atoms of the alkyl sulfate ester salt and the alkyl benzene sulfonate salt is, for example, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, or 22, and may be within a range between any two of the values ​​exemplified here.

[0030] The content of the emulsifier per 100 parts by mass of the chloroprene polymer can be 0.5 to 8.0 parts by mass. The content of the emulsifier is, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5.0, 5, 5.5, 6.0, 6.5, 7.0, 7.5, or 8.0 parts by mass, and may be within a range between any two of the values ​​exemplified here. By setting the content of the emulsifier within the above range, a chloroprene polymer latex can be obtained that has excellent mechanical stability and excellent rubber recovery efficiency by freezing or the like. Furthermore, by adjusting the amount of the emulsifier, the ratio of the micelle surface area to the amount of emulsifier can be adjusted.

[0031] 1.3 Characteristics of Chloroprene Polymer Latex The chloroprene polymer latex according to the present invention comprises micelles containing the above-mentioned chloroprene polymer and an emulsifier. When a volume-based particle size distribution of micelles in the range of 1 nm to 10,000 nm is measured by dynamic light scattering to obtain a histogram, the chloroprene polymer latex according to the present invention has a ratio of micelle surface area to emulsifier amount calculated by a specific formula using values ​​obtained from the histogram, which falls within a specific range.

[0032] The particle size distribution can be measured by an apparatus capable of measurement by dynamic light scattering (for example, ELSZ Series (manufactured by Otsuka Electronics Co., Ltd.)) using a test solution prepared by diluting the chloroprene polymer latex with distilled water so that the solid content concentration becomes 0.01% by mass. The histogram has 45 classes obtained by dividing the horizontal axis into 45 equal parts in the range of 1 nm to 10,000 nm, with the horizontal axis representing the particle diameter (nm) expressed in common logarithm. The vertical axis of the histogram represents the volume distribution. When the "micelle surface area per emulsifier molecule" of the chloroprene polymer latex according to the present invention is calculated using the particle diameter class value of each class of the histogram and the volume distribution of each class, the ratio of the micelle surface area to the amount of emulsifier defined by the following formula, the micelle surface area per emulsifier molecule is 0.40 (nm ２ / emulsifier molecule) more than 1.20 (nm ２ / 1 molecule of emulsifier).

[0033] The micelle surface area per emulsifier molecule is, for example, 0.41, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, or 1.15 nm ２ / one molecule of emulsifier, and may be within a range between any two of the values ​​exemplified here.

[0034] In the above formula, d ｋ represents the particle size class value (nm) of the particle size class k, which is the kth smallest particle size. Here, the class value can be the median value of each class. For example, if the range of class k is "X ｋ That's all, Y ｋIf "less than" then d ｋ is X ｋ and Y ｋ It can be calculated as the average value of V ｋ is the volume distribution of class k, and the volume distribution of class k having the kth smallest particle diameter, i.e., the value on the vertical axis, can be used. The total of the volume distributions of all classes is 1, and the volume distribution of each class k is expressed as a numerical value between 0 and 1. S is the solid content ratio of the chloroprene polymer latex. S is expressed as a numerical value between 0 and 1. S is the ratio of the solid content of the chloroprene polymer latex to the chloroprene polymer latex, and is expressed as a numerical value between 0 and 1. ρ Ｌｘ is the specific gravity (g / cm) of the chloroprene polymer latex ３ ) and can be determined from the mass per unit volume of the chloroprene polymer latex measured at 25°C. ＣＲ is the specific gravity (g / cm) of the chloroprene polymer at 25°C ３ ) and when the chloroprene-based polymer is a chloroprene homopolymer, it is 1.21 g / cm ３ n is the amount (mol) of emulsifier contained in 1 L of chloroprene polymer latex. Ａ Avogadro's number is 6.02 x 10 ２３ mol －１ This can be done.

[0035] The above formula is derived as follows: For class k of the particle size distribution, the "particle volume per micelle in class k" and the "volume of class k in 1 L of micelles" are as follows: Particle volume per micelle in class k: 4 / 3 × π × (d ｋ / 2) ３ = 1 / 6 × π × d ｋ ３ (nm) Volume of class k in 1 L of micelles: 1000 x V ｋ(mL) For class k of the particle size distribution, the value obtained by dividing the "volume of class k in 1 L of micelles" by the "particle volume per micelle in class k" is defined as the "number of micelles contained in class k per 1 L of micelles." Number of micelles contained in class k per 1 L of micelles: 6 x 10 ２４ ×V ｋ / π×d ｋ ３ The "micelle surface area per micelle in class k" is expressed as follows: Micelle surface area per micelle in class k: 4 × π(d ｋ / 2) ２ = πd ｋ ２ Next, the value obtained by multiplying the "micelle surface area per micelle in class k" by the "number of micelles contained in class k per 1 L of micelles" is defined as the "micelle surface area of ​​class k per 1 L of micelles." Micelle surface area of ​​class k per 1 L of micelles: 6 × 10 ２４ ×V ｋ / d ｋ (nm ２ The "volume of all micelles per 1 L of chloroprene polymer latex (including all classes)" is expressed as follows: Volume of all micelles per 1 L of chloroprene polymer latex: 1×ρ ＬＸ / ρ ＣＲ × S = ρ ＬＸ ×S / ρ ＣＲ (L) "The surface area of ​​micelles contained in class k per 1 L of chloroprene polymer latex" is defined as the value obtained by multiplying "the volume of all micelles per 1 L of chloroprene polymer latex" by "the surface area of ​​micelles of class k per 1 L of micelles". Surface area of ​​micelles contained in class k per 1 L of chloroprene polymer latex: 1×ρ ＬＸ xS x 6 x 10 ２４ ×V ｋ / ρ ＣＲ ×d ｋFurther, a numerical value obtained by accumulating "surface area of ​​micelles contained in class k per 1 L of chloroprene polymer latex" for all classes is defined as "surface area of ​​micelles per 1 L of chloroprene polymer latex."

[0036] The numerical value obtained by dividing the "surface area of ​​micelles per 1 L of chloroprene polymer latex" by the "amount n (mol) of emulsifier contained in 1 L of chloroprene polymer latex" is defined as the "surface area of ​​micelles per molecule of emulsifier".

[0037] Specifically, the "micelle surface area per emulsifier molecule" can be calculated by the method described in the Examples.

[0038] According to the present invention, by setting the "micelle surface area per emulsifier molecule" within the above-mentioned range, it is presumed that the dispersibility and stability of the chloroprene polymer latex can be appropriately adjusted, resulting in a chloroprene polymer latex that is excellent in mechanical stability and rubber recovery efficiency by freezing or the like. The "micelle surface area per emulsifier molecule" can be controlled by carefully adjusting the production conditions of the chloroprene polymer latex. Specifically, it can be controlled by carefully adjusting the particle size of the monomer droplets in the production conditions of the chloroprene polymer latex, as well as the amount and timing of addition of the emulsifier.

[0039] The chloroprene polymer latex according to one embodiment of the present invention has a "micelle surface area per 1 L of chloroprene polymer latex" calculated by the above formula of 30,000 to 100,000 m ２ The "surface area of ​​micelles per 1 L of chloroprene polymer latex" can be, for example, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, or 100,000 m ２ and may be in a range between any two of the values ​​given here.

[0040] The chloroprene polymer latex according to one embodiment of the present invention preferably has a D50 value obtained from the particle size distribution of 50 to 300 nm. D50 may be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255, 260, 265, 270, 275, 280, 285, 290, 295, or 300 nm, or may be within a range between any two of the values ​​exemplified here.

[0041] D50 can be determined from the particle size distribution, specifically by the method described in the Examples. The "surface area of ​​micelles per liter of chloroprene polymer latex," or D50, can be controlled by carefully adjusting the production conditions of the chloroprene polymer latex. Specifically, it can be controlled by carefully adjusting the particle size of the monomer droplets in the production conditions of the chloroprene polymer latex, as well as the amount and timing of addition of the emulsifier.

[0042] In the chloroprene polymer latex according to one embodiment of the present invention, D80-D20 obtained from the particle size distribution is preferably 0.05 to 0.30 nm. D80-D20 is, for example, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or 0.30 nm, and may be within a range between any two of the values ​​exemplified here.

[0043] D80-D20 can be determined from the particle size distribution, specifically by the method described in the Examples. The "surface area of ​​micelles per liter of chloroprene polymer latex," D80-D20, can be controlled by carefully adjusting the production conditions of the chloroprene polymer latex. Specifically, it can be controlled by carefully adjusting the particle size of the monomer droplets in the production conditions of the chloroprene polymer latex, as well as the amount and timing of addition of the emulsifier.

[0044] The chloroprene polymer latex according to one embodiment of the present invention preferably has an aggregate generation rate of 0.5 to 25.0% in a mechanical stability test measured under conditions of a load of 1.0 kg, a rotation speed of 1000 rpm, and a time period of 10 minutes. The aggregate generation rate is, for example, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20.0, 21.0, 22.0, 23.0, 24.0, or 25.0%, and may be within a range between any two of the values ​​exemplified here.

[0045] The aggregate generation rate of the chloroprene polymer latex can be determined by the method described in the Examples. The aggregate generation rate of the chloroprene polymer latex according to one embodiment of the present invention can be controlled by adjusting the "micelle surface area per emulsifier molecule" by highly adjusting the production conditions of the chloroprene polymer latex. When the aggregate generation rate of the chloroprene polymer latex according to one embodiment of the present invention is equal to or less than the above upper limit, the stability during the production process, storage, and transportation is excellent, and when the aggregate generation rate is equal to or more than the above lower limit, the rubber component can be recovered more efficiently.

[0046] The chloroprene polymer latex according to one embodiment of the present invention preferably has a film-forming rate of 50% or more. The film-forming rate may be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100%, and may be within a range between any two of the values ​​exemplified here. The film-forming rate of the chloroprene polymer latex according to one embodiment of the present invention can be controlled by adjusting the "micelle surface area per emulsifier molecule" by carefully adjusting the production conditions of the chloroprene polymer latex. The film-forming rate can be determined by the method described in the Examples. When the chloroprene polymer latex according to one embodiment of the present invention has a film-forming rate equal to or higher than the lower limit, the rubber component can be recovered more efficiently.

[0047] The solid content concentration of the chloroprene polymer latex according to one embodiment of the present invention is, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90% by mass, and may be within a range between any two of the values ​​exemplified here.

[0048] 2. Method for Producing Chloroprene Polymer Latex The method for producing a chloroprene polymer latex according to the present invention is not particularly limited. A method for producing a chloroprene polymer latex according to one embodiment of the present invention may include a monomer droplet micronization step, a polymerization step, and an emulsifier additional addition step. In the monomer droplet micronization step, droplets containing raw monomers, including a chloroprene monomer, are micronized until the average particle size of the droplets is 300 nm or less by colliding the raw monomer droplets with a collision medium in the presence of an initially added emulsifier. In the polymerization step, the raw monomers, including the chloroprene monomer, are polymerized to obtain a chloroprene polymer. In the emulsifier additional addition step, an additional emulsifier is additionally added after the monomer droplet micronization step and after the initiation of polymerization. Here, the amount of the additional emulsifier is 10 to 60% by mass relative to 100% by mass of the total of the initially added emulsifier and the additional emulsifier. Mini-emulsion polymerization may be employed in the production method according to one embodiment of the present invention.

[0049] <Stock Solution Preparation Step> A method for producing a chloroprene polymer latex according to one embodiment of the present invention may include a stock solution preparation step. The stock solution may contain a chloroprene-containing starting monomer, an emulsifier, and water, and may also contain a chain transfer agent, an initiator, and a hydrophobe. In the stock solution preparation step, the chloroprene-containing starting monomer, an emulsifier, and optionally a molecular weight modifier, an initiator, a hydrophobe, and the like are added to water to prepare the stock solution. Alternatively, in the stock solution preparation step, an emulsifier may be added to water to prepare a soap solution, and the chloroprene-containing starting monomer is added with a molecular weight modifier, a hydrophobe, and optionally an initiator to prepare an oil phase mixture solution, and the soap solution and the oil phase mixture solution are mixed to obtain the stock solution. The initiator may be added during the preparation of the oil phase mixture solution or after the micronization step. When an oil-soluble initiator is used, it is preferably added during the preparation of the oil phase mixture solution, and when a water-soluble initiator is used, it may also be added after the micronization step.

[0050] Examples of the emulsifier include the types of emulsifiers described above. As described below, a production method according to one embodiment of the present invention may include an additional emulsifier addition step. The emulsifier added during preparation of the raw material solution is referred to as an initially added emulsifier, and the emulsifier added in the additional addition step is referred to as an additionally added emulsifier. The amount of the initially added emulsifier added may be 0.5 to 4.0 parts by mass per 100 parts by mass of the raw material monomers including the chloroprene monomer. The amount of the initially added emulsifier added per 100 parts by mass of the raw material monomers including the chloroprene monomer may be, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, or 4.0 parts by mass, and may be within a range between any two of the values ​​exemplified here. The amount of the initially added emulsifier relative to the total of the initially added emulsifier and the additionally added emulsifier (100% by mass) may be 40 to 90% by mass, for example, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90% by mass, and may be within a range between any two of the values ​​exemplified here. The total of the initially added emulsifier and the additionally added emulsifier may be the total amount of emulsifiers used in producing the chloroprene polymer latex.

[0051] The molecular weight modifier is not particularly limited, and known molecular weight modifiers commonly used in chloroprene polymerization can be used, such as mercaptan compounds such as dodecyl mercaptan, xanthogen compounds, dithiocarbonate compounds, trithiocarbonate compounds, and carbamate compounds. The amount of molecular weight modifier added per 100 parts by mass of raw material monomers including chloroprene monomer is, for example, 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 parts by mass, and may be within a range between any two of the values ​​exemplified here.

[0052] The initiator is not particularly limited, and known polymerization initiators commonly used in the polymerization of chloroprene can be used. Examples of polymerization initiators include potassium persulfate, ammonium persulfate, sodium persulfate, benzoyl peroxide, hydrogen peroxide, water-soluble azo compounds such as 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), oil-soluble azo compounds such as 2,2'-azobisisobutyronitrile, water-soluble organic peroxides such as t-butyl hydroperoxide, and oil-soluble organic peroxides such as 1,1,3,3-tetramethylbutyl-2-ethylhexanoate. The amount of initiator added per 100 parts by mass of raw material monomers including the chloroprene monomer is, for example, 0.01, 0.05, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 parts by mass, and may be within a range between any two of the values ​​exemplified here.

[0053] The hydrophobe is not particularly limited, and a compound having low solubility in water can be appropriately used, such as a long-chain alkyl compound such as hexadecane, heptadecane, octadecane, nonadecane, etc. The amount of hydrophobe added relative to 100 parts by mass of the raw material monomers including the chloroprene monomer is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0054] <Monomer Droplet Micronization Process> In the monomer droplet micronization process, droplets containing raw material monomers, including chloroprene monomers, are micronized until the average particle size of the droplets is 300 nm or less by colliding the raw material monomer droplets with a collision medium in the presence of an initially added emulsifier. Examples of the collision medium include other monomer droplets, raw material solutions such as solvents (water), ceramic balls, etc. Micronization methods can be performed using known devices, such as ultrasonic homogenizers, stirring homogenizers, high-pressure homogenizers, and wet-type micronization devices. One example is the Violamo ultrasonic homogenizer (SONICSTAR 85). When using an ultrasonic homogenizer, it is believed that the raw material solution (including monomer droplets, water, etc.) generated by vacuum collides with the monomer droplets, resulting in micronization of the monomer droplets. For example, the output of the homogenizer may be, for example, 10, 50, 100, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, or 5000 W, or may be within a range between any two of the values ​​exemplified here. Furthermore, the processing time (time for performing the micronization process) of the ultrasonic homogenizer may be, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 minutes, or may be within a range between any two of the values ​​exemplified here.

[0055] An example of such a homogenizer is a stirring homogenizer (e.g., AS ONE Corporation, Digital Type AHG-160D). The rotation speed of the stirring homogenizer is, for example, 300, 1000, 5000, 10000, 15000, 20000, 25000, or 30000 rpm, and may be within a range between any two of the values ​​exemplified here.

[0056] Another example is the Starburst series manufactured by Sugino Machine Co., Ltd. In this device, it is believed that the monomer droplets are atomized by collision between ceramic balls or a raw material solution (including monomer droplets, water, etc.). The pressure in the atomization process is, for example, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, or 245 MPa, and may be within a range between any two of the values ​​exemplified here.

[0057] In the monomer droplet micronization step, the monomer droplets are preferably micronized to an average particle size of 300 nm or less. The average particle size of the monomer droplets after the monomer droplet micronization step is, for example, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, or 300 nm, or may be within a range between any two of the values ​​exemplified here. The average particle size of the monomer droplets can be determined by the method described in the Examples. By micronizing the monomer droplets so that the average particle size falls within the above-mentioned range, a chloroprene polymer latex with better mechanical stability can be obtained.

[0058] <Polymerization Step> In the polymerization step, raw material monomers including chloroprene monomers are polymerized to obtain a chloroprene-based polymer. The polymerization may at least partially begin when the raw material monomers and the initiator are brought into contact in the raw material solution preparation step. Alternatively, the polymerization step may be initiated by adding an initiator after the monomer droplet microparticulation step, without adding a polymerization initiator in the raw material solution preparation step. In one embodiment of the present invention, after the monomer droplet microparticulation step, the temperature of the microparticulated raw material solution is adjusted and polymerization is carried out for a desired period of time. The polymerization temperature is not particularly limited and may be, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50°C, or may be within a range between any two of the values ​​exemplified herein. The polymerization time is not particularly limited and may be, for example, 0, 10, 20, 30, 40, 50, or 60 hours, or may be within a range between any two of the values ​​exemplified herein.

[0059] The final conversion rate of the raw material monomer is not particularly limited, but may be, for example, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95%, or may be within a range between any two of the values ​​exemplified here. To adjust the final conversion rate, a polymerization terminator may be added to terminate the polymerization reaction when the desired conversion rate is reached.

[0060] The polymerization terminator is not particularly limited, and a known polymerization terminator commonly used in the polymerization of chloroprene can be used. Examples of the polymerization terminator include phenothiazine (thiodiphenylamine), 4-t-butylcatechol, and 2,2-methylenebis-4-methyl-6-t-butylphenol. After the polymerization step is completed, an unreacted monomer removal step can be carried out, in which unreacted monomers remaining after the emulsion polymerization are removed by a conventional method such as reduced pressure distillation.

[0061] <Additional Emulsifier Addition Step> In one embodiment of the present invention, the additional emulsifier addition step can be carried out after the monomer droplet micronization step. The additional emulsifier addition step can be carried out after the start of the polymerization step, after the polymerization step is completed, or after the unreacted monomer removal step. In one embodiment of the present invention, the raw material solution preparation step, monomer droplet micronization step, polymerization step, unreacted monomer removal step, and additional emulsifier addition step can be carried out in this order. In the additional emulsifier addition step, an additionally added emulsifier is additionally added at least after the monomer droplet micronization step. Here, the amount of the additionally added emulsifier relative to the total of the initially added emulsifier and the additionally added emulsifier (100% by mass) is 10 to 60% by mass. The amount of the additionally added emulsifier relative to 100% by mass of the total of the initially added emulsifier and the additionally added emulsifier is, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60% by mass, and may be within a range between any two of the values ​​exemplified herein. The amount of the additionally added emulsifier added may be 0.5 to 4.0 parts by mass relative to 100 parts by mass of the raw material monomers including the chloroprene monomer. The amount of the additionally added emulsifier added relative to 100 parts by mass of the raw material monomers including the chloroprene monomer is, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, or 4.0 parts by mass, and may be within a range between any two of the values ​​exemplified herein.

[0062] Furthermore, to the chloroprene polymer latex obtained by the production method according to one embodiment of the present invention, after polymerization, any additive such as a freeze stabilizer, an emulsion stabilizer, a viscosity modifier, an antioxidant, or a preservative may be added, as long as the effects of the present invention are not impaired.

[0063] 3. Rubber Component of Chloroprene Polymer Latex One embodiment of the present invention relates to the rubber component of the chloroprene polymer described above. There are no particular limitations on the method for obtaining the rubber component of the chloroprene polymer latex. For example, the rubber component of the chloroprene polymer can be obtained by mixing the chloroprene polymer latex with a large amount of methanol, precipitating, filtering, and drying. For example, the rubber component of the chloroprene polymer can be obtained by freeze-drying the chloroprene polymer latex. Specifically, the rubber component of the chloroprene polymer can be obtained by adjusting the pH of the chloroprene polymer latex, freeze-drying it, washing it with water, and drying it with hot air. The rubber component of the chloroprene polymer includes a methanol precipitate of the chloroprene polymer latex and a freeze-dried product of the chloroprene polymer latex.

[0064] 4. Rubber Composition A rubber composition according to one embodiment of the present invention includes the rubber component described above. In addition to the rubber component described above, the rubber composition according to the present invention may include, as necessary, a vulcanizing agent, a vulcanization accelerator, an antioxidant, a filler, a reinforcing material, a silane coupling agent, a plasticizer, a softener, a lubricant, and a processing aid, and may further include components such as a stabilizer, a flame retardant, and a vulcanization retarder, as long as the effects of the present invention are not impaired.

[0065] 4.1 Vulcanizing Agent The rubber composition according to the present invention may contain a vulcanizing agent. The type of vulcanizing agent is not particularly limited as long as it does not impair the effects of the present invention. The vulcanizing agent is preferably a vulcanizing agent that can be used to vulcanize chloroprene-based rubber. One or more vulcanizing agents can be freely selected and used. Examples of vulcanizing agents include sulfur, zinc oxide, and organic peroxides.

[0066] An example of the metal oxide is zinc oxide. The metal oxide preferably contains zinc oxide, and more preferably is zinc oxide.

[0067] Examples of organic peroxides include dicumyl peroxide, benzoyl peroxide, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, diisobutyryl peroxide, cumyl peroxyneodecanoate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, di(4-t-butylcyclohexyl)peroxydicarbonate, and di(2-ethylhexyl)peroxydicarbonate. butylperoxyneodecanoate, t-butylperoxyneoheptanoate, t-hexylperoxypivalate, t-butylperoxypivalate, di(3,5,5-trimethylhexanoyl)peroxide, dilauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, disuccinic acid peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, t-hexylperoxy peroxy-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, t-butylperoxy-2-ethylhexanoate, di(3-methylbenzoyl) peroxide, benzoyl(3-methylbenzoyl) peroxide, dibenzoyl peroxide, 1,1-di(t-butylperoxy)-2-methylcyclohexane, 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 2, 2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, 2,Examples of such peroxides include 2-di-(t-butylperoxy)butane, t-butyl peroxybenzoate, n-butyl 4,4-di-(t-butylperoxy)valerate, 1,4-bis[(t-butylperoxy)isopropyl]benzene, di-t-hexyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide. Among these, at least one selected from dicumyl peroxide, 1,4-bis[(t-butylperoxy)isopropyl]benzene, t-butyl-α-cumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3 is preferred, and 1,4-bis[(t-butylperoxy)isopropyl]benzene is particularly preferred.

[0068] From the viewpoint of ensuring processing safety and obtaining a good vulcanizate, the rubber composition according to the present invention preferably contains 3 to 15 parts by mass of a vulcanizing agent relative to the rubber component contained in the rubber composition. The content of the vulcanizing agent is, for example, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts by mass relative to 100 parts by mass of the rubber component contained in the rubber composition, and may be within a range between any two of the numerical values ​​exemplified here.

[0069] 4.2 Acid Acceptor The rubber composition according to one embodiment of the present invention may contain an acid acceptor. Examples of the acid acceptor include magnesium oxide, lead oxide, trimead tetroxide, iron trioxide, titanium dioxide, calcium oxide, and hydrotalcite. As the hydrotalcite, one represented by the following formula can be used: [M ２＋ １－ｘ M ３＋ ｘ (OH) ２ ] ｘ＋ [A ｎ－ｘ／ｎ ・mH２ O] ｘ－

[0070] In the above formula, M ２＋ : Mg ２＋ , Zn ２＋ At least one divalent metal ion M selected from ３＋ :Al ３＋ , Fe ３＋ At least one trivalent metal ion selected from the following: ｎ－ :Co ３ ２－ , Cl ― , NO ３ ２－ At least one n-type anion selected from the following: X: 0<X≦0.33.

[0071] As the hydrotalcite, Mg ４．３ Al ２ (OH) １２．６ CO ３ ・3.5H ２ O, Mg ３ ZnAl ２ (OH) １２ CO ３ ・3H ２ O, Mg ４．５ Al ２ (OH) １３ CO ３ ・3.5H ２ O, Mg ４．５ Al ２ (OH) １３ CO ３ , Mg ４ Al ２ (OH) １２ CO ３ ・3.5H ２ O, Mg ６ Al ２ (OH) １６ CO ３ ・4H ２ O, Mg ５ Al ２ (OH) １４ CO ３ ・4H ２ O, Mg ３ Al ２ (OH) １０ CO ３ ・1.7H２ O, and particularly preferably Mg ４．３ Al ２ (OH) １２．６ CO ３ ・3.5H ２ O, Mg ３ ZnAl ２ (OH) １２ CO ３ ・3H ２ It is O.

[0072] The amount of the acid acceptor added may be 0.1 to 15 parts by mass per 100 parts by mass of the rubber component. The amount of the hydrotalcite added may be, for example, 0.1, 0.2, 0.3, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here. The hydrotalcites may be used alone or in combination of two or more.

[0073] 4.3 Vulcanization Accelerator The rubber composition according to the present invention may contain a vulcanization accelerator, and may contain 0.3 to 5.0 parts by mass of the vulcanization accelerator per 100 parts by mass of the rubber composition contained in the rubber composition. The content of the vulcanization accelerator is, for example, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 parts by mass, and may be within a range between any two of the values ​​exemplified here. Note that the rubber composition according to the present invention may not contain a vulcanization accelerator.

[0074] The type of vulcanization accelerator is not particularly limited as long as it does not impair the effects of the present invention. The vulcanization accelerator is preferably a vulcanization accelerator that can be used for vulcanizing chloroprene-based rubber. One or more vulcanization accelerators can be freely selected and used. Examples of vulcanization accelerators include thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenate-based, and thiazole-based accelerators.

[0075] Examples of thiuram vulcanization accelerators include tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, tetramethylthiuram monosulfide, dipentamethylenethiuram tetrasulfide, etc. Examples of dithiocarbamate vulcanization accelerators include sodium dibutyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, copper dimethyldithiocarbamate, ferric dimethyldithiocarbamate, tellurium diethyldithiocarbamate, etc. Examples of thiourea-based vulcanization accelerators include thiourea compounds such as ethylene thiourea, diethyl thiourea (N,N'-diethyl thiourea), trimethyl thiourea, diphenyl thiourea (N,N'-diphenyl thiourea), and 1,3-trimethylene-2-thiourea. Examples of guanidine-based vulcanization accelerators include 1,3-diphenyl guanidine, 1,3-di-o-tolyl guanidine, 1-o-tolyl biguanide, and di-o-tolyl guanidine salt of dicatechol borate. Examples of xanthate-based vulcanization accelerators include zinc butyl xanthogenate and zinc isopropyl xanthogenate. Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, 2-mercaptobenzothiazole zinc salt, 2-mercaptobenzothiazole cyclohexylamine salt, 2-(4'-morpholinodithio)benzothiazole, N-cyclohexylbenzothiazole-2-sulfenamide, etc. These may be used alone or in combination of two or more.

[0076] 4.4 Filler (Reinforcing Material) The rubber composition according to the present invention may contain a filler. Examples of the filler (reinforcing material) include furnace carbon black such as SAF, ISAF, HAF, EPC, XCF, FEF, GPF, HMF, and SRF, modified carbon black such as hydrophilic carbon black, thermal carbon such as channel black, lamp black, FT, and MT, acetylene black, ketjen black, silica, clay, talc, and calcium carbonate. These may be used alone or in combination of two or more.

[0077] A rubber composition according to one embodiment of the present invention may contain 5 to 130 parts by mass of a filler per 100 parts by mass of the rubber component. The filler content may be, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, or 130 parts by mass, or may be within a range between any two of the values ​​exemplified here. By containing the filler content within the above range, the rubber composition according to one embodiment of the present invention can appropriately adjust the hardness of the vulcanized molded product.

[0078] 4.5 Silane Coupling Agent The rubber composition according to one embodiment of the present invention may contain a silane coupling agent. When the rubber composition according to one embodiment of the present invention contains silica as a filler, it preferably contains a silane coupling agent. The silane coupling agent is not particularly limited, and those used in commercially available rubber compositions can be used, for example, vinyl coupling agents, epoxy coupling agents, styryl coupling agents, methacrylic coupling agents, acrylic coupling agents, amino coupling agents, polysulfide coupling agents, and mercapto coupling agents. In particular, from the viewpoint of scorch resistance and reinforcing effect, vinyl coupling agents, methacrylic coupling agents, and acrylic coupling agents, which initiate reaction under high temperature conditions during crosslinking, are preferred.

[0079] The rubber composition according to one embodiment of the present invention may contain 0.5 to 15 parts by mass of a silane coupling agent per 100 parts by mass of silica contained in the rubber composition, for example, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts by mass, or may be within a range between any two of the values ​​exemplified here. These may be used alone or in combination of two or more. By including the above-mentioned silane coupling agent and setting the content of the silane coupling agent within the above-mentioned range, the dispersibility of the silica filler in the rubber and the reinforcing effect between the rubber and the silica filler can be improved, and the occurrence of scorch can be suppressed.

[0080] 4.6 Plasticizer The plasticizer is not particularly limited as long as it is compatible with the chloroprene polymer rubber. Examples include vegetable oils such as rapeseed oil, phthalate plasticizers, dioctyl sebacate (DOS), dibutyl sebacate (DBS), dioctyl adipate (DOA), ester plasticizers, ether-ester plasticizers, thioether plasticizers, aromatic oils, and naphthenic oils. These may be used alone or in combination of two or more. The amount of plasticizer added may be 0 to 50 parts by mass per 100 parts by mass of the rubber component contained in the rubber composition, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 parts by mass, and may be within a range between any two of the values ​​exemplified here.

[0081] 4.7 Lubricants and Processing Aids The rubber composition according to the present invention may further contain a lubricant and / or a processing aid. Lubricants and processing aids are added primarily to improve processability, such as by facilitating release of the rubber composition from rolls, molding dies, extruder screws, etc. Examples of lubricants and processing aids include fatty acids such as stearic acid, paraffin-based processing aids such as polyethylene, fatty acid amides, petrolatum, and factice. These may be used alone or in combination of two or more. The rubber composition according to the present invention may contain 0.5 to 15 parts by mass of lubricant and processing aid per 100 parts by mass of the rubber component, and may also contain 1 to 10 parts by mass. The content of the lubricant and processing aid may be, for example, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts by mass, or may fall within a range between any two of the values ​​exemplified herein.

[0082] 4.8 Others In addition to the above-mentioned components, the rubber composition according to the present invention may further contain components such as antioxidants, antioxidants, flame retardants, and vulcanization retarders, as long as the effects of the present invention are not impaired. Examples of antioxidants and antioxidants include ozone antioxidants, phenolic antioxidants, amine antioxidants, acrylate antioxidants, imidazole antioxidants, aromatic secondary amine antioxidants, carbamic acid metal salts, waxes, phosphorus-based antioxidants, and sulfur-based antioxidants. Examples of imidazole antioxidants include 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, and zinc salts of 2-mercaptobenzimidazole. The rubber composition according to the present invention may contain a total of 0.1 to 10 parts by mass of antioxidants and antioxidants per 100 parts by mass of the rubber component contained in the rubber composition.

[0083] 5. Method for Producing Rubber Composition The rubber composition according to one embodiment of the present invention can be obtained by kneading a rubber component of a chloroprene polymer latex and other necessary components at a temperature not higher than the vulcanization temperature. Examples of devices for kneading the raw material components include conventionally known kneading devices such as a mixer, a Banbury mixer, a kneader mixer, and an open roll.

[0084] 6. Unvulcanized molded body, vulcanized product, and vulcanized molded body The unvulcanized molded body according to one embodiment of the present invention uses the rubber composition according to one embodiment of the present invention, and is a molded body (molded article) of the rubber composition (unvulcanized state) according to one embodiment of the present invention. A method for producing an unvulcanized molded body according to one embodiment of the present invention includes a step of molding the rubber composition (unvulcanized state) according to one embodiment of the present invention. The unvulcanized molded body according to one embodiment of the present invention is made of the rubber composition (unvulcanized state) according to one embodiment of the present invention.

[0085] A vulcanizate according to one embodiment of the present invention is a vulcanizate of the rubber composition according to one embodiment of the present invention. A method for producing a vulcanizate according to one embodiment of the present invention includes a step of vulcanizing the rubber composition according to one embodiment of the present invention.

[0086] A vulcanization molded article according to one embodiment of the present invention is a vulcanization molded article of a rubber composition according to one embodiment of the present invention. The vulcanization molded article according to one embodiment of the present invention uses a vulcanizate according to one embodiment of the present invention and is a molded article (molded product) of the vulcanizate according to one embodiment of the present invention. The vulcanization molded article according to one embodiment of the present invention is made of a vulcanizate according to one embodiment of the present invention.

[0087] The vulcanized molded article according to one embodiment of the present invention can be obtained by molding a vulcanizate obtained by vulcanizing the rubber composition (unvulcanized state) according to one embodiment of the present invention, and can also be obtained by vulcanizing a molded article obtained by molding the rubber composition (unvulcanized state) according to one embodiment of the present invention. The vulcanized molded article according to one embodiment of the present invention can be obtained by vulcanizing the rubber composition according to one embodiment of the present invention after molding or during molding. A method for producing a vulcanized molded article according to one embodiment of the present invention comprises a step of molding a vulcanized article according to one embodiment of the present invention, or a step of vulcanizing an unvulcanized molded article according to one embodiment of the present invention.

[0088] The unvulcanized molded article, vulcanized product, and vulcanized molded article according to one embodiment of the present invention can be used as rubber parts in various industrial fields, such as buildings, structures, ships, railways, coal mines, and automobiles. The rubber composition, vulcanized product, and vulcanized molded article according to one embodiment of the present invention can be used as rubber parts in various industrial fields, such as buildings, structures, ships, railways, coal mines, and automobiles, and can be used for rubber parts such as automotive rubber members (e.g., automotive seals), hose materials, rubber molds, gaskets, rubber rolls, industrial cables, industrial conveyor belts, and sponges. In particular, they can be used as any of transmission belts, conveyor belts, hoses, wipers, immersion products, sealing parts, adhesives, boots, rubber-coated fabrics, rubber rolls, vibration-proof rubber, and sponge products.

[0089] (Automotive Rubber Components) Automotive rubber components include gaskets, oil seals, and packings, which are components used in machines and devices to prevent the leakage of liquids and gases and the intrusion of debris and foreign objects such as rainwater and dust into the interior. Specifically, there are gaskets used for fixed applications and oil seals and packings used for moving parts. Gaskets whose sealing parts are fixed with bolts or the like use various materials depending on the purpose, as opposed to soft gaskets such as O-rings and rubber sheets. Furthermore, packings are used for rotating parts such as shafts of pumps and motors, moving parts of valves, reciprocating parts such as pistons, connecting parts of couplers, and water stop parts of water faucets. The rubber composition according to one embodiment of the present invention can be used in the manufacture of automotive parts.

[0090] (Hose Material) A hose material is a bendable tube, and specifically includes high-pressure and low-pressure hoses for water supply, oil supply, air supply, steam supply, hydraulic pressure, etc. The rubber composition according to one embodiment of the present invention can be used to produce the hose material.

[0091] (Rubber molded article) Examples of rubber molded articles include anti-vibration rubber, vibration-damping materials, boots, etc. Anti-vibration rubber and vibration-damping materials are rubbers that prevent the transmission and spread of vibrations. Specific examples include torsional dampers, engine mounts, muffler hangers, etc. for automobiles and various other vehicles that absorb vibrations during engine operation to prevent noise. The rubber composition according to one embodiment of the present invention can be used to manufacture anti-vibration rubber and vibration-damping materials. Boots are bellows-shaped members whose outer diameter gradually increases from one end to the other. Specific examples include boots for constant velocity joint covers, boots for ball joint covers (dust cover boots), and boots for rack and pinion gears that protect drive parts such as automobile drive systems. The rubber composition according to one embodiment of the present invention can be used to manufacture boots.

[0092] (Gaskets, etc.) Gaskets, oil seals, and packings are components in machines and devices that prevent the leakage of liquids and gases and the intrusion of debris and foreign objects such as rainwater and dust into the interior. Specifically, there are gaskets used for fixed applications and oil seals and packings used for moving parts. Gaskets in which the sealing part is fixed with bolts or the like use various materials depending on the purpose, as opposed to soft gaskets such as O-rings and rubber sheets. Furthermore, packings are used for rotating parts such as shafts of pumps and motors, moving parts of valves, reciprocating parts such as pistons, connecting parts of couplers, and water stop parts of water faucets. The rubber composition according to one embodiment of the present invention can be used to manufacture sealing members.

[0093] (Rubber Roll) A rubber roll is manufactured by adhesively coating a metal core such as an iron core with rubber, and is generally manufactured by spirally winding a rubber sheet around a metal iron core. Rubber materials such as NBR, EPDM, and CR are used for rubber rolls depending on the required characteristics of various applications, such as papermaking, various metal manufacturing, film manufacturing, printing, general industrial use, agricultural machinery such as rice hullers, and food processing. CR has good mechanical strength that can withstand the friction of the object being conveyed, and is therefore used in a wide range of rubber roll applications. Furthermore, rubber rolls that convey heavy objects have the problem of deformation under load, and improvements are needed. The rubber composition according to one embodiment of the present invention can be used to manufacture rubber rolls.

[0094] (Industrial Cable) Industrial cables are linear components for transmitting electrical or optical signals. They are made by covering a good conductor such as copper or a copper alloy, or an optical fiber, with an insulating covering layer, and a wide variety of industrial cables are manufactured depending on their structure and installation location. The rubber composition according to one embodiment of the present invention can be used to manufacture industrial cables.

[0095] (Industrial Conveyor Belts) Industrial conveyor belts are made of rubber, resin, and metal, and are selected to suit a wide variety of uses. Among these, rubber conveyor belts are inexpensive and widely used, but when used in environments where there is a lot of friction and collision with the transported objects, they have been prone to damage due to deterioration. The rubber composition according to one embodiment of the present invention can be used to manufacture industrial conveyor belts.

[0096] (Sponge) Sponge is a porous material with countless fine pores inside, and is specifically used in vibration-damping materials, sponge seal parts, wetsuits, shoes, etc. The rubber composition according to the present invention uses a chloroprene polymer rubber, which makes it possible to enhance the flame retardancy of the sponge. The rubber composition according to one embodiment of the present invention can be used to manufacture a sponge, and a sponge with excellent flame retardancy can be manufactured. Furthermore, the hardness of the resulting sponge can be appropriately adjusted by adjusting the content of the foaming agent, etc.

[0097] Methods for molding the rubber composition (unvulcanized state) and vulcanized product according to one embodiment of the present invention include press molding, extrusion molding, calendar molding, etc. The temperature for vulcanizing the rubber composition may be appropriately set in accordance with the composition of the rubber composition, and may be 140 to 220°C or 160 to 190°C. The vulcanization time for vulcanizing the rubber composition may be appropriately set depending on the composition of the rubber composition, the shape of the unvulcanized molded product, etc.

[0098] The present invention will be described in more detail below based on examples, but the present invention should not be construed as being limited to these examples.

[0099] Example 1 Raw Material Solution Preparation Step A soap solution was prepared by dissolving 0.433 g of sodium lauryl sulfate (SDS) in 100 g of pure water. 1.25 g of hexadecane, 0.008 g of dodecyl mercaptan, and 0.0748 g of initiator 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) were dissolved in 25 g of chloroprene monomer to prepare an oil phase mixed solution. The soap solution and oil phase mixed solution were transferred to a 500 ml beaker to obtain a raw material solution.

[0100] <Monomer droplet micronization step, polymerization step, and emulsifier addition step> The raw material solution was pre-stirred for 10 minutes with a mechanical stirrer under ice cooling, and then emulsified for 10 minutes using a Violamo ultrasonic homogenizer (SONICSTAR 85) at 100% output (maximum high-frequency output: 85 W, oscillation frequency 21 kHz ± 1 kHz). The average particle size of the droplets containing the chloroprene monomer was 150 nm. The average particle size of the droplets can be measured by diluting the polymerization solution with distilled water to a solids concentration of 0.01% by mass and using an ELSZ Series (manufactured by Otsuka Electronics Co., Ltd.). The average particle size of the polymerization solution can be determined by the cumulant method using the autocorrelation function obtained by photon correlation spectroscopy in dynamic light scattering. The resulting emulsion was transferred to a 500 ml four-neck separable flask and polymerization was carried out at 30°C under stirring with a mechanical stirrer. The temperature of the polymerization liquid was raised to 30° C., and polymerization was carried out for 12 hours. After removing the monomer from the obtained emulsion under reduced pressure, 0.433 g of sodium lauryl sulfate (SDS) was further added to obtain a chloroprene polymer latex.

[0101] (Examples 2 to 4, Comparative Examples 1 and 2) Chloroprene polymer latexes were obtained in the same manner as in Example 1, except that the type of emulsifier, the apparatus used in the monomer droplet micronization step, and the amount of emulsifier added in the emulsifier additional addition step were as shown in Table 1. In Example 3, a stirring homogenizer (AHG-160D, manufactured by AS ONE Co., Ltd.) was used, and in Example 4, a high-pressure homogenizer (Starburst Mini, manufactured by Sugino Machine Co., Ltd.) was used. In Example 2, sodium dodecylbenzenesulfonate (DBS) was used as the emulsifier.

[0102] <Volume-based particle size distribution of micelles> The chloroprene polymer latex was diluted with distilled water to a solids concentration of 0.01% by mass, and the volume-based particle size distribution of the micelles was measured in the range of 1 nm to 10,000 nm using an ELSZ Series (manufactured by Otsuka Electronics Co., Ltd.) to obtain a histogram. The histogram has 45 classes obtained by dividing the range of 1 nm to 10,000 nm into 45 equal parts on the horizontal axis, and the vertical axis represents the volume distribution.

[0103] Using the particle size class values ​​of each class of the histogram and the volume distribution of each class, the micelle surface area per molecule of the emulsifier was calculated according to the following formula:

[0104] In the above formula, d ｋ represents the class value (nm) of the particle diameter of the class k where the particle diameter is the kth smallest, and the class value is the median value of the class. For example, if the range of class k is "X ｋ That's all, Y ｋ If "less than" then d ｋ is X ｋ and Y ｋ is the average value of V ｋis the volume distribution of class k, and the sediment distribution of class k having the kth smallest particle diameter, i.e., the value on the vertical axis, is used. The total of the volume distributions of all classes is 1, and the volume distribution of each class k is expressed as a numerical value between 0 and 1. s is the solid content ratio of the chloroprene polymer latex. S is the ratio of the solid content of the chloroprene polymer latex to the chloroprene polymer latex, and is expressed as a numerical value between 0 and 1. ρ Ｌｘ is the specific gravity (g / cm) of the chloroprene polymer latex ３ ) and was calculated from the mass per unit volume of the chloroprene polymer latex measured at 25°C. ＣＲ is the specific gravity (g / cm) of the chloroprene polymer at 25°C ３ ) and 1.21 g / cm ３ n is the amount (mol) of emulsifier contained in 1 L of chloroprene polymer latex. Ａ Avogadro's number is 6.02 x 10 ２３ mol －１ It was decided.

[0105] Furthermore, from the particle size distribution, the average particle diameter (D50, cumulative 50% diameter) and D80 (cumulative 80% diameter) - D20 (cumulative 20% diameter) were calculated.

[0106] <Mechanical Stability> Using a Marlon testing apparatus, a shear force of 1.0 kg load and 1,000 rpm was applied to 50 g of a chloroprene polymer latex adjusted to a solids concentration of 60% by mass for 10 minutes, and the amount of aggregates generated was evaluated. After applying the shear force under the above conditions, the aggregates attached to the rotor of the Marlon testing apparatus were collected on a SUS80 mesh wire screen, washed with pure water, dried under reduced pressure, and then their mass was measured. The aggregate generation rate was calculated from the measured dry mass of the aggregates using the following formula to serve as an index of mechanical stability. A smaller value for the aggregate generation rate indicates better stability against shear forces and better mechanical stability. Aggregate generation rate (mechanical stability) (mass %) = dry mass of aggregates [g] / solid mass of chloroprene polymer latex [g] × 100

[0107] The rate of occurrence of aggregates (mechanical stability) was evaluated according to the following evaluation criteria: ○: 25% or less ×: more than 25%

[0108] <Freeze-forming property> 200 g of a chloroprene polymer latex having a solid content concentration of 40% by mass was frozen at -20°C to obtain a sheet having a thickness of 0.2 mm, and the amount of chloroprene polymer (rubber) obtained after washing the sheet with warm water at 40°C was evaluated. The freeze-forming rate was calculated from the measured amount of chloroprene polymer (rubber) using the following formula. A higher freeze-forming rate indicates that the rubber can be recovered more efficiently by demulsification through freezing. Freeze-forming rate (mass%) = Amount of chloroprene polymer (rubber) obtained by freeze-drying [g] / Mass of solid content of chloroprene polymer latex [g] × 100. Good: 50% or more. Bad: Less than 50%.

[0109]

Claims

1. A chloroprene polymer latex containing micelles containing a chloroprene polymer and an emulsifier, wherein the volume-based particle size distribution of the micelles is measured by dynamic light scattering in the range of 1 nm to 10,000 nm to obtain a histogram, the horizontal axis of the histogram representing particle diameters expressed in common logarithms, the horizontal axis having 45 classes obtained by dividing the range of 1 nm to 10,000 nm into 45 equal classes, and the vertical axis representing volume distribution, and the class value of the particle diameter of the class k having the kth smallest particle diameter is represented by d ｋ nm The volume distribution of class k is V ｋ , the solid content of the chloroprene polymer latex is S, and the specific gravity of the chloroprene polymer latex is ρ Ｌｘ g / cm ３ , the specific gravity of the chloroprene polymer is ρ ＣＲ g / cm ３ The amount of emulsifier contained in 1 L of the chloroprene polymer latex is n mol, Avogadro's number is N Ａ A chloroprene polymer latex which satisfies the following formula when 2. The chloroprene polymer latex according to claim 1, wherein D50 obtained from the particle size distribution is 50 to 300 nm.

3. The chloroprene polymer latex according to claim 1 or 2, wherein the content of the emulsifier per 100 parts by mass of the chloroprene polymer is 0.5 to 8.0 parts by mass.

4. The chloroprene polymer latex according to claim 1 or 2, wherein the rate of aggregate formation is 0.5 to 25.0% in a mechanical stability test measured under conditions of a load of 1.0 kg, a rotation speed of 1000 rpm, and a time period of 10 minutes.

5. The chloroprene polymer latex according to claim 1 or 2, wherein the micelle surface area per 1 L of the chloroprene polymer latex is 30,000 to 100,000 m ２ A chloroprene polymer latex.

6. A rubber component of the chloroprene polymer latex according to claim 1 or 2.

7. A rubber composition comprising the rubber component according to claim 6.

8. A vulcanized molded article comprising the rubber composition according to claim 7.

9. The vulcanized molded article according to claim 8, which is any one of a transmission belt, a conveyor belt, a hose, a wiper, a dipping product, a sealing part, an adhesive, a boot, a rubber-coated fabric, a rubber roll, a vibration-proof rubber, and a sponge product.

10. A method for producing a chloroprene polymer latex containing micelles containing a chloroprene polymer and an emulsifier, the method comprising: a monomer droplet micronization step, a polymerization step, and an emulsifier additional addition step; in the monomer droplet micronization step, droplets containing a raw material monomer including a chloroprene monomer are collided with a collision medium in the presence of an initially added emulsifier to micronize the droplets until the average particle size of the droplets is 300 nm or less; in the polymerization step, the raw material monomer including the chloroprene monomer is polymerized to obtain a chloroprene polymer; and in the emulsifier additional addition step, an additional emulsifier is additionally added after the monomer droplet micronization step, and the amount of the additional emulsifier is 10 to 60% by mass relative to 100% by mass of the total of the initially added emulsifier and the additional emulsifier.

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